1. Field of the Invention
This invention relates to an amorphous magnetic alloy, and more particularly to an amorphous magnetic alloy suitable as material for a magnetic head for a recording and/or reproducing apparatus.
2. Description of the Prior Art
As high permeability magnetic material, there are hitherto known a polycrystalline Fe-Ni alloy, a polycrystalline Fe-Al-Si alloy, a single-crystalline ferrite and a polycrystalline ferrite. However, from the view-point of material for the magnetic head, the Fe-Ni alloy (Permalloy group) has so low saturation magnetic flux density as at most 8000 gauss, and it is inferior in wear resistance. Moreover, its permeability is remarkably reduced in the high frequency region. On the other hand, the Fe-Al-Si alloy (Sen-dust) has a higher saturation magnetic flux density as about 10000 gauss, and further it is superior in wear resistance. However, the Fe-Al-Si alloy cannot be plasticly worked at all. And the saturation magnetic flux density of ferrite is at most 4500 gauss. Higher saturation magnetic flux density than 4500 gauss cannot be expected for ferrite because of its magnetic interaction.
As above described, the conventional high permeability magnetic materials have both merits and demerits. It is difficult to use them as materials for magnetic heads able to cope with high-density recording and high-quality recording to be expected here-after.
Generally, it is considered that constituent atoms are not latticed in an amorphous metal, and so it has not crystalline magnetic anisotropy. From this viewpoint, amorphous metal can be expected to be a magnetically soft material which has a low coercive force and high permability. However, an amorphous material containing, for example, only Fe as metal element, or containing Fe as the main component and Co and/or Ni as residual components, has a very large magnetostriction constant .lambda.. Accordingly, it has the disadvantage that its initial permeability is low from the relation-ship of .mu..varies.1/.lambda..sigma. (.sigma.: internal and external stress). When such material is annealed at a suitable temperature below the crystallization temperature, its permeability is much increased. However, when such material is used as material for magnetic head, a head tip should be fixed with molded resin. The head tip is much tensioned with the hardening resin. As the result of the combination of such tension and magnetostriction coefficient, induced magnetic anisotropy is generated in the head tip. Accordingly, the permeability of the head tip material becomes again low, resulting in the decrease of the output of the magnetic head. The reason is considered to be that the magnetostriction coefficient of the amorphous metal containing mainly Fe is large. Accordingly, in order to obtain a magnetic head material whose magnetic characteristics are not deteriorated by working processes, its magnetostriction coefficient should be as low as possible.